Depends on the hybrid tea.Some are more tender than others.
I've planted mine with the bud union some 4-6 inches deep. Over the years that portion of the bush below ground and above the bud union forms it's own roots.
I still provide some protection with shredded oak leaves. They die back to the protection but soon grow back and bloom at their normal end of May, first of June, times.
Other than the leaves, I do nothing. I have a couple of dozen or so hybrid teas left from the 300 varieties I had 5 years ago.
They've all been replaced with hardy shrubs.
If you expect a big hybrid tea rose garden using no winter protection in our zone, you'll be disappointed.
A few members of our society in my area have big hybrid tea gardens but they use rose collars religiously each year to protect them.
You'll have to change your rose preferences or be prepared to do some work each spring and fall.

Own-root vs grafted makes no difference in the hardiness of the rose above the ground. Since they will die back pretty much to the soil line unless you do some sort of winter protection, and are in a climate where winter protection is effective, what matters is vigor. Understocks provide vigor.

If you are having trouble with the roses completely dying off, instead of failing to thrive, either you like yellow :-), or the bud unions aren't ending up deep enough. Burying the bud union is el cheapo winter protection that works. However, I have found around here it can be difficult to convince people of that because of the general rule to plant a potting plant at the level it is growing in the pot. Potted roses are usually planted very high to make as much room as possible in the pot for the roots. It is then up to the buyer to understand that the entire contraption has to then be buried.

Here, even when the winters were much, much colder, I've had little trouble getting hybrid teas to survive winter. The problem has always come getting that little speck of life to amount to anything. I like big roses that produce a lot of flowers, and a hybrid tea just isn't going to do that around here.

Perhaps your problem is thinking your plant is dead when it only needs pruning to the mulch line and some time to recover. I say that because I can't remember losing a rose (HT or other) to winter in many years. I am in a hard winter area for roses, very little snow, harsh winds, temps to -30 below.

If you want HT's I would suggest you make sure your soil is excellent, keep the plant in peak health thru out the season, plant deep, dump on a couple bags of cedar mulch NOT before Thanksgiving, and prune the canes to the mulch line in spring and then WAIT and see if they don't regrow.

If what you want are roses that don't die back and leaf out from last season's canes--check out the Canadian roses.

Bean, I was just wondering why you said NOT before Thanksgiving?

Thanks for the input. Some of my old grafted teas make it through every winter and bloom beautifully (my first experimental K Mart purchases about 10 years ago.... Angel Face, Queen Elizabeth, and a couple I can't remember their names). My roses are mulched, fertilized, sprayed, and pampered, and I am not quick to expect them to leaf out in spring and think they are dead, so that's not the problem, Bean Counter. I lost Octoberfest and Rosie O'Donnell to the Easter freeze this year. Wow...didn't realize Rockford was Zone 4, I'm around Peoria, Bean Counter.

I have had problems with own root roses dying including Austins, Romanticas, and Bucks. Some of the survivors stay very small. Surprisingly, I got an own root Graham Thomas at Walmart a few years ago in a 1 gallon pot and it has bounced back nicely. Canadian roses have underwhelming bloom form and are not fragrant (excepting rugosa hybrids) - you are better off with Ramblin' Red. Some Bucks, like Earthsong, Quietness, Aunt Honey and Prairie Sunrise will do quite nicely. Abraham Darby is another Austin that bounces back and Frederic Mistral is a hardy Romantica. Sharifa Asma is very hardy. Old Garden roses that have survived in my garden include Rose de Rescht, Jacques Cartier and Baronne Prevost.